In order to free minerals from the base materials with which the minerals are associated, many different processes have been devised and used. Usually ore processing involves crushing or grinding steps in order to reduce the particle size of the total material charge. The particle size reduction steps in both wet and dry ore beneficiation processes are in general intended to free the mineral values from the gangue materials so that a differential separation thereof can be accomplished. The present dry type ore processing method and apparatus is intended for use to free valuable minerals from sedimentary type deposits. Many ores of substantial value are, of course, found in sedimentary deposits or in common types of sedimentary materials. Due to the nature of such deposits, the minerals or values often do not occur in well defined locations or even in substantial concentration. Minerals of substantial value, such as uranium, vanadium, copper, gold and the like, can actually be widely dispersed in such sedimentary deposits. Since the minerals are of substantial value, areas and deposits where the minerals are concentrated have been extensively worked, and ores that are of adequate value to justify the expenses of mining, hauling and treatment have been removed and shipped to mill sites for treatment.
Under circumstances where the mineral values of ore deposits at a site are of varied concentration and parts of the deposit are uneconomic to haul to remote mills for processing, the deposits have been selectively mined, or low value materials that are removed have been sorted to avoid shipment of lower grade materials. Large dumps at the mine sites may, accordingly, contain substantial quantities of mineral, but it is generally still uneconomic to extract such low grade materials through use of on-site milling practices. At many mine sites the water necessary for wet mineral extraction processes is not even available. Accordingly, even portable types of wet ore processing equipment cannot be used.
Dumps containing uranium ores present a special problem, inasmuch as the radiation level at a dump site may be raised above prescribed environmental levels even though the percentage concentration of uranium in the material at the dump is still inadequate to justify the expenses of transportation and mill treatment.
The present invention is directed to the problems outlined, inasmuch as a method and apparatus is set forth which will permit processing of ores at remote mine site locations. Since a dry process is provided, dumps in arid regions at many remote locations can be processed. Likewise, ores that have been left in place due to previous costs of extraction, transportation and treatment can now be utilized, since practice of the present invention at the mine site provides a low treatment cost and a greatly reduced transportation burden. The present process and apparatus is especially adapted for use in the beneficiation of ores of the sedimentary type. In such deposits the mineral values are generally dispersed throughout gangue materials that are predominantly grains of sand. The minerals have been washed and silted into intimate contact with the grains of sand. A cementing material that may itself be of mineral origin holds the grains of sand and mineral together. Accordingly, the mineral values are essentially coated on the external surface of discrete grains of sand, and while the mineral may be tightly held in cracks and crevices on the surface of the individual sand grains, the mineral does not actually intrude into the sand or chemically combine therewith but remains separate therefrom. Efficient treatment of such ores requires reduction of the sandstone conglomerate to a particle size corresponding to the size of the individual sand grains and subsequent treatment of the total materials to dissolve, wipe, wash or otherwise remove the mineral ore and stains thereof from the exterior surface of the sand grain.
Usually the sand itself is not of commercial significance especially when located at a remote site, and, accordingly, the sand is generally considered to be the gangue material that is to be discarded. From a weight and bulk standpoint, it is this sand constituent that comprises the predominant portion of any deposit. Accordingly, if the mineral values alone or inclusive of the cementitious binder or slimes associated with the mineral values can be separated from the sand, the cost of transportation and haulage will be substantially reduced. Any on-site preliminary process that will separate the values from gangue materials is of further benefit, since the actual extraction of the mineral values from binder and carrier components at a flotation, chemical or other type processing mill will itself be improved by the mine site upgrading operations.